Lecture 9 – Locomotion: Flight. Powered flight has evolved several times:. Pterosaurs. Insects. Birds. Powered Flight : Bats. Supported by digits 2-5. Skin - patagium. Generation of Lift. Turbulent Flow. Laminar flow – parallel movement of air streams .
Powered flight has evolved several times:
Supported by digits 2-5
Skin - patagium
Laminar flow – parallel movement of air streams
Velocity across top is higher than bottom.
P is air pressure.
Cis a constant.
dis the density of air, and V is velocity.
Lift = P(Lower) – P(Upper)
Myotislucifugus (l.b.bat)- 20 MPH
Eptesicusfuscus (b.b.bat)- 40 MPH
Tadaridabrasiliensis (Brazilian free-tailed bat) – up to 60 MPH
1. Increase camber, or curvature of the wing.
2. Increase angle of attack (even a symmetric airfoil can generate lift this way)
3. Alter wing size and shape.
Wing loading: Body weight /surface area.
Body Weight Surface Area Wing Load
House wren 11.0 g 48.4 cm2 0.24 g/ cm2
Glossophaga 10.6 g 99.3 cm2 0.11 g/ cm2
Myotis4.2 g 67.6 cm2 0.06 g/ cm2
b. Aspect ratio - length / width
Tadarida– high aspect ratio
Artibeus – low aspect ratio
Greater tuberosity of humerus
Eumopsperotiswestern bonneted bat
Modest greater tuberosity
* Situation similar in phyllostomids
Sac-winged bats – Emballonuridae.
Keeled manubrium of sternum.
Some (Natalidae) have rigid axial skeleton.
1. Compressed thoracic vertebrae - not fused, but very tightly interconnecting
2. Fused sacral vertebrae and fused lumbar vertebrae